Battery electric vehicles (BEVs) include a fraction battery that is rechargeable from an external electric power source and powers the electric machine. Hybrid electric vehicles (HEVs) include an internal combustion engine, one or more electric machines, and a fraction battery that at least partially powers the electric machine. Plug-in hybrid electric vehicles (PHEVs) are similar to HEVs but the traction battery in a PHEV is capable of recharging from an external electric power source. These vehicles are examples of vehicles that are capable of being at least partially driven by an electric machine that is coupled to a traction battery via a high voltage DC bus.
In these vehicles, certain events require discharging of the DC bus quickly, such as key-off events, in which a controller in the vehicle activates the discharge of the DC bus. The discharging reduces the DC bus voltage to an amount to prevent issues. It is therefore desirable for the discharging to start and finish as quickly as possible.